Attenuation Effects of Alpha-Pinene Inhalation on Mice with Dizocilpine-Induced Psychiatric-Like Behaviour

Medicinal plants and plant-based traditional medicine: Alternative treatments for depression and their potential mechanisms of action

Background

Clinical depression is a serious public health issue that affects 4.7 % of the world's population and can lead to suicide tendencies. Although drug medications are available, only 60 % of the depressed patients respond positively to the treatments, while the rest experience side effects that resulted in the discontinuation of their medication. Thus, there is an urgent need for developing a new anti-depressant with a distinct mode of action and manageable side effects. One of the options is using medicinal plants or plant-based traditional medicine as alternative therapies for psychiatric disorders.

Objectives

Therefore, the objective of this review was twofold; to identify and critically evaluate anti-depressant properties of medicinal plants or those incorporated in traditional medicine; and to discuss their possible mechanism of action as well as challenges and way forward for this alternative treatment approach.

Methods

Relevant research articles were retrieved from various databases, including Scopus, PubMed, and Web of Science, for the period from 2018 to 2020, and the search was updated in September 2024. The inclusion criterion was relevance to antidepressants, while the exclusion criteria included duplicates, lack of full-text availability, and non-English publications.

Results

Through an extensive literature review, more than 40 medicinal plant species with antidepressant effects were identified, some of which are part of traditional medicine. The list of the said plant species included Albizia zygia (DC.) J.F.Macbr., Calculus bovis Sativus, Celastrus paniculatus Willd., Cinnamomum sp., Erythrina velutina Willd., Ficus platyphylla Delile, Garcinia mangostana Linn., Hyptis martiusii Benth, and Polygonum multiflorum Thunb. Anti-depressant mechanisms associated with those plants were further characterised based on their modes of action such as anti-oxidation system, anti-inflammation action, modulation of various neurotransmitters, neuroprotective effect, the regulation of hypothalamic-pituitary-adrenal (HPA) axis and anti-depressant mechanism. The challenges and future outlook of this alternative and complementary medicine are also explored and discussed.

Conclusion

This pool of identified plant species is hoped to offer health care professionals the best possible alternatives of anti-depressants from natural phytocompounds that are efficacious, safe and affordable for applications in future clinical settings.

Neuroprotective effects of alpha-pinene against behavioral deficits in ketamine-induced mice model of schizophrenia: Focusing on oxidative stress status

Schizophrenia (SCZ) is a profound neurological disorder that affects approximately 1% of the global population. Alpha-pinene (α-pinene) is a natural and active monoterpene found in coniferous tree oil, primarily pine, with diverse pharmacological characteristics, including antioxidative, anxiolytic, and antidepressant properties. This research study delves into the neuroprotective effects of α-pinene on oxidative stress, memory deficits, and depressive and anxiety-like behaviors in a ketamine-induced mice model of SCZ using male mice. The mice were randomly divided into six groups: vehicle, control, positive control, ketamine, α-pinene at 50 mg/kg, and α-pinene at 100 mg/kg. Treatment of the ketamine-induced mice model of SCZ with α-pinene yielded significant improvements in depressive and anxiety-like behaviors and cognitive impairments. Furthermore, it significantly elevated glutathione (GSH) levels, total antioxidant capacity (TAC), dopamine levels, catalase (CAT), and superoxide dismutase (SOD) activities while markedly reducing malondialdehyde (MDA) levels. The current study establishes that α-pinene treatment effectively mitigates oxidative damage, cognitive deficits, and depressive and anxiogenic-like behaviors in the brains of ketamine-treated mice. Therefore, α-pinene treatment is an efficacious approach to forestall the neurobehavioral and neurobiochemical adverse effects of the ketamine-induced SCZ model of mice.

Neuropharmacological Effects of Terpenoids on Preclinical Animal Models of Psychiatric Disorders: A Review

Terpenoids are widely distributed in nature, especially in the plant kingdom, and exhibit diverse pharmacological activities. In recent years, screening has revealed a wide variety of new terpenoids that are active against different psychiatric disorders. This review synthesized the current published preclinical studies of terpenoid use in psychiatric disorders. This review was extensively investigated to provide empirical evidence regarding the neuropharmacological effects of the vast group of terpenoids in translational models of psychiatric disorders, their relevant mechanisms of action, and treatment regimens with evidence of the safety and psychotropic efficacy. Therefore, we utilized nine (9) electronic databases and performed manual searches of each. The relevant data were retrieved from the articles published until present. We used the search terms "terpenoids" or "terpenes" and "psychiatric disorders" ("psychiatric disorders" OR "psychiatric diseases" OR "neuropsychiatric disorders" OR "psychosis" OR "psychiatric symptoms"). The efficacy of terpenoids or biosynthetic compounds in the terpenoid group was demonstrated in preclinical animal studies. Ginsenosides, bacosides, oleanolic acid, asiatic acid, boswellic acid, mono- and diterpenes, and different forms of saponins and triterpenoids were found to be important bioactive compounds in several preclinical studies of psychosis. Taken together, the findings of the present review indicate that natural terpenoids and their derivatives could achieve remarkable success as an alternative therapeutic option for alleviating the core or associated behavioral features of psychiatric disorders.

Pinus halepensis Essential Oil Ameliorates Aβ1-42-Induced Brain Injury by Diminishing Anxiety, Oxidative Stress, and Neuroinflammation in Rats

The Pinus L. genus comprises around 250 species, being popular worldwide for their medicinal and aromatic properties. The present study aimed to evaluate the P. halepensis Mill. essential oil (PNO) in an Alzheimer’s disease (AD) environment as an anxiolytic and antidepressant agent. The AD-like symptoms were induced in Wistar male rats by intracerebroventricular administration of amyloid beta1-42 (Aβ1-42), and PNO (1% and 3%) was delivered to Aβ1-42 pre-treated rats via inhalation route for 21 consecutive days, 30 min before behavioral assessments. The obtained results indicate PNO’s potential to relieve anxious–depressive features and to restore redox imbalance in the rats exhibiting AD-like neuropsychiatric impairments. Moreover, PNO presented beneficial effects against neuroinflammation and neuroapoptosis in the Aβ1-42 rat AD model.

Prenatal exposure to α-pinine improves reflexive motor behaviours in mice offspring

α-pinene is a well-known compound representative of the monoterpenes group with a wide range of pharmacological activities. This article aims to determine effects of the prenatal exposure to α-pinene on reflexive motor behaviours in mice offspring. Forty pregnant female NMRI mice (8-10 weeks old) were allocated into four groups. Group 1 served as control and groups 2-4 were intraperitoneally (i.p.) injected α-pinene (0.1, 0.5 and 1 mg/kg) on 5, 8, 11, 14 and 17 days of gestation (GD). The control group was injected with saline at the same days. Following delivery, 20 pups from each litter were selected and reflexive motor behaviours determined using ambulation, hindlimb foot angle, surface righting, hindlimb strength, grip strength, front-limb suspension and negative geotaxis tests. Based on the findings of the present study, maternal exposure to α-pinene increased ambulation score, hind-limb suspension score, grip strength, front-limb suspension compared with the control group (P < 0.05). Also, prenatal exposure to α-pinene decreased surface righting, hind-limb foot angle and negative geotaxis in mice offspring compared with the control group (P < 0.05). α-pinene (0.1, 0.5 and 1 mg/kg) decreased blood MDA and increased SOD and GPx levels in mice offspring (P < 0.05). These results suggested α-pinene exposure during pregnancy has positive effect on reflexive motor behaviours in mice offspring possibly due to its antioxidant properties.

Investigation of the protective effect of resveratrol in an MK-801-induced mouse model of schizophrenia

Increasing evidence supports the view that oxidative stress and brain demyelination play an important role in the pathogenesis of schizophrenia. Resveratrol is a powerful antioxidant with neuroprotective effects. This study aimed to assess the effect of resveratrol on schizophrenia-like behaviors and possible brain demyelination induced by MK-801, an N-methyl-D-aspartate glutamate receptor antagonist, and the underlying neuroprotective mechanism. Resveratrol (40 mg/kg/day/, intraperitoneal) was administered to mice for 14 days. MK-801 (1 mg/kg/day, intraperitoneal) was injected into the mice 4 h after the resveratrol administration for 14 days. The open-field and elevated-plus maze tests were performed to detect behavior changes on the 15th day. Following the behavioral tests, the expression of the myelin basic protein (MBP) was measured with the real-time PCR (RT-PCR) method, while total oxidant capacity (TOS) and total antioxidant capacity (TAS), which are the biomarkers of oxidative damage, were measured with the ELISA method. Hematoxylin-eosin staining was also used to identify stereological and pathological changes in the brain. According to the results obtained, this study showed for the first time that resveratrol prevented glial cell infiltration induced in the brain by MK-801 and shrinkage of nerve cell nuclei in the hippocampus and corpus callosum. However, the resveratrol administrations did not correct behavioral disorders and demyelination of schizophrenia. Although resveratrol partially prevented oxidative damage in the brain in the mice that were injected with MK-801, it was determined that this effect was not statistically significant. These results showed that resveratrol administration partially protects tissues against MK-801-induced neurodegeneration, and resveratrol may be used in combination with different antioxidants or at different doses in future studies.

Essential Oils of New Lippia alba Genotypes Analyzed by Flow-Modulated Comprehensive Two-Dimensional Gas Chromatography (GC×GC) and Chemometric Analysis

Lippia alba (Mill.) N. E. Br. (Verbenaceae) is an aromatic shrub whose essential oils have stood out as a promising source for application in several industrial fields. In this study, the essential oils chemical characterization of eight new L. alba genotypes was performed. The selected materials were collected from the Active Germplasm Bank of the Agronomic Institute and the essential oils were extracted by hydrodistillation. Flow-modulated comprehensive two-dimensional gas chromatography coupled to mass spectrometry (GC×GC-MS) was employed for chemical characterization and evaluation of possible co-eluted compounds. In addition, the chemical analyses were submitted to multivariate statistical analyses. From this investigation, 73 metabolites were identified in the essential oils of the genotypes, from which α-pinene, β-myrcene, 1,8-cineole, linalool, neral, geranial, and caryophyllene oxide were the most abundant compounds among the accessions. This is the first report disclosing α-pinene in higher amounts in L. alba (19.69%). In addition, sabinene, trans-verbenol, myrtenol, (E)-caryophyllene, α-guaiene, germacrene D, and α-bulnesene were also found in relevant quantities in some of the genotypes, and myrtenal and myrtenol could be well separated through the second dimension. Such results contributed to the understanding of the chemical composition of those new genotypes, being important to drive a future industrial applicability and studies in genetic breeding.

Potential Herb-Drug Interactions in the Management of Age-Related Cognitive Dysfunction

Late-life mild cognitive impairment and dementia represent a significant burden on healthcare systems and a unique challenge to medicine due to the currently limited treatment options. Plant phytochemicals have been considered in alternative, or complementary, prevention and treatment strategies. Herbals are consumed as such, or as food supplements, whose consumption has recently increased. However, these products are not exempt from adverse effects and pharmacological interactions, presenting a special risk in aged, polymedicated individuals. Understanding pharmacokinetic and pharmacodynamic interactions is warranted to avoid undesirable adverse drug reactions, which may result in unwanted side-effects or therapeutic failure. The present study reviews the potential interactions between selected bioactive compounds (170) used by seniors for cognitive enhancement and representative drugs of 10 pharmacotherapeutic classes commonly prescribed to the middle-aged adults, often multimorbid and polymedicated, to anticipate and prevent risks arising from their co-administration. A literature review was conducted to identify mutual targets affected (inhibition/induction/substrate), the frequency of which was taken as a measure of potential interaction. Although a limited number of drugs were studied, from this work, interaction with other drugs affecting the same targets may be anticipated and prevented, constituting a valuable tool for healthcare professionals in clinical practice.

Alpha-pinene and dizocilpine (MK-801) attenuate kindling development and astrocytosis in an experimental mouse model of epilepsy

Understanding the molecular and cellular mechanisms involved during the onset of epilepsy is crucial for elucidating the overall mechanism of epileptogenesis and therapeutic strategies. Previous studies, using a pentylenetetrazole (PTZ)-induced kindling mouse model, showed that astrocyte activation and an increase in perineuronal nets (PNNs) and extracellular matrix (ECM) molecules occurred within the hippocampus. However, the mechanisms of initiation and suppression of these changes, remain unclear. Herein, we analyzed the attenuation of astrocyte activation caused by dizocilpine (MK-801) administration, as well as the anticonvulsant effect of α-pinene on seizures and production of ECM molecules. Our results showed that MK-801 significantly reduced kindling acquisition, while α-pinene treatment prevented an increase in seizures incidences. Both MK-801 and α-pinene administration attenuated astrocyte activation by PTZ and significantly attenuated the increase in ECM molecules. Our results indicate that astrocyte activation and an increase in ECM may contribute to epileptogenesis and suggest that MK-801 and α-pinene may prevent epileptic seizures by suppressing astrocyte activation and ECM molecule production.

Forest Volatile Organic Compounds and Their Effects on Human Health: A State-of-the-Art Review

The aim of this research work is to analyze the chemistry and diversity of forest VOCs (volatile organic compounds) and to outline their evidence-based effects on health. This research work was designed as a narrative overview of the scientific literature. Inhaling forest VOCs like limonene and pinene can result in useful antioxidant and anti-inflammatory effects on the airways, and the pharmacological activity of some terpenes absorbed through inhalation may be also beneficial to promote brain functions by decreasing mental fatigue, inducing relaxation, and improving cognitive performance and mood. The tree composition can markedly influence the concentration of specific VOCs in the forest air, which also exhibits cyclic diurnal variations. Moreover, beneficial psychological and physiological effects of visiting a forest cannot be solely attributed to VOC inhalation but are due to a global and integrated stimulation of the five senses, induced by all specific characteristics of the natural environment, with the visual component probably playing a fundamental role in the overall effect. Globally, these findings can have useful implications for individual wellbeing, public health, and landscape design. Further clinical and environmental studies are advised, since the majority of the existing evidence is derived from laboratory findings.

Terpenoids, Cannabimimetic Ligands, beyond the Cannabis Plant

Medicinal use of Cannabis sativa L. has an extensive history and it was essential in the discovery of phytocannabinoids, including the Cannabis major psychoactive compound-Δ9-tetrahydrocannabinol (Δ9-THC)-as well as the G-protein-coupled cannabinoid receptors (CBR), named cannabinoid receptor type-1 (CB1R) and cannabinoid receptor type-2 (CB2R), both part of the now known endocannabinoid system (ECS). Cannabinoids is a vast term that defines several compounds that have been characterized in three categories: (i) endogenous, (ii) synthetic, and (iii) phytocannabinoids, and are able to modulate the CBR and ECS. Particularly, phytocannabinoids are natural terpenoids or phenolic compounds derived from Cannabis sativa. However, these terpenoids and phenolic compounds can also be derived from other plants (non-cannabinoids) and still induce cannabinoid-like properties. Cannabimimetic ligands, beyond the Cannabis plant, can act as CBR agonists or antagonists, or ECS enzyme inhibitors, besides being able of playing a role in immune-mediated inflammatory and infectious diseases, neuroinflammatory, neurological, and neurodegenerative diseases, as well as in cancer, and autoimmunity by itself. In this review, we summarize and critically highlight past, present, and future progress on the understanding of the role of cannabinoid-like molecules, mainly terpenes, as prospective therapeutics for different pathological conditions.